The two-year trial of Hong Kong’s first electric buses has been suspended for the third time in nine months due to tyre problems.

New World Services Holdings, which owns franchised bus companies Citybus and New World First Bus, confirmed on Wednesday that five electric buses were recalled in mid-September after drivers and district councillors raised concerns about tyres slipping in wet weather.

This is the third time the trial has been halted since it started in late December. The five buses were the first to hit the road after the government allocated HK$180 million to purchase 36 electric buses for the city’s transport companies in a bid to improve roadside air quality and reduce greenhouse gas emissions from petrol-driven buses.

Registered engineer and mechanics expert Lo Kok-keung said the frequent check-ups and recalls showed the buses were “quite problematic”.

“The check-ups carried out by the manufacturer cannot be good enough, or why would the buses be recalled again and again after being recalled the first time,” he said.

According to New World Services, the manufacturer of the five recalled buses – Shenzhen-based BYD – has improved the braking system to address “occasional slipping problems’’, but the buses would only return to service again after “thorough checks”.

The five buses are running on Hong Kong Island routes 11, 12, 25A, 78 and 81.

In addition to these buses, a second batch of five electric buses manufactured by Shandong- based Great Dragon International Corporation was also recalled before they hit the road.

The bus company confirmed that they were recalled because of problems with the stop bell. This means none of the firm’s 10 vehicles are now in use.

A total of 22 complaints were received about the five buses since their launch. They were mainly about air conditioning.

Eleven cases involving malfunctions and six traffic accidents involving the five buses were recorded in the same period, but the bus company said all were “minor incidents and were not caused by mechanical faults”.

Up to last month, the first batch of buses spent 55 days with the manufacturer – or 21 per cent of the total number of days since the trial was launched.

A BYD spokesman told the Post that the five buses that were recalled went through a “software upgrading process” and were now ready for use again.

“We did not encounter tyre slippage problems with BYD electric buses used elsewhere. The problem occurred for the first time in Hong Kong ,” the spokesman said.

Another company, Kowloon Motor Bus, put one BYD-made electric bus on trial for half a year in 2013, but it failed and was returned to the manufacturer.